Apparatus for making fat free potato chips

ABSTRACT

A continuous process for making fat-free potato chips without using any cooking oil whatsoever. Chipping potatoes are prepared, sliced, continuously monolayered onto a conveyer and squeegeed to remove the excess starch and moisture. The slices are initial cooked on independently controlled conveyers in a primary 3-zone oven where they are first radiant heated and then subjected to two stages of forced air convection heating by driving the air into both surfaces of the slices simultaneously as the moisture content is reduced to 15%. The slices are then final cooked in a dielectric heater where an even controlled heat is applied in two tandem drying zones where the potato slices are subjected to long wavelength (65.8 ft.) radio frequency (15 mhz) waves from two 20 kw transmitters which reduce the moisture content of the finished slices to 7%. The finished potato chips are seasoned and packaged and have the texture, appearance and mouthfeel of deep-fat fried potato chips.

This is a divisional of application Ser. No. 08/168,640 filed on Dec.16, 1993, now U.S. Pat. No. 5,470,600.

FIELDS OF THE INVENTION

The present invention relates generally to a method and apparatus ofcooking foodstuffs, and, more particularly, to making fat-free potatochips by radiant heating, forced air heating and radio frequency waveheating.

DISCUSSION OF BACKGROUND AND PRIOR ART a. Fats

Edible fats and oils ("fats") are organic compounds composed of threefatty acids attached to the glycerol molecule and are also known astriglycerides. Major types of fatty acids are saturated, polyunsaturatedand monounsaturated.

The body needs a small amount of fats to carry fat soluble vitamins, tostore energy, to cushion and protect vital organs, to insulate the bodythermally, to give shape to the body and to regulate cellularmetabolism. Non-essential fatty acids are made by the body itself, butessential fatty acids must be obtained dietetically through the foods weeat. But, fatty foods are high in calories (9 calories per gram of fat)and too much dietetic fat is bad for many reasons.

It is now well recognized and generally accepted, as demonstrated andproven by numerous scientific studies, that there is a closerelationship between the amount of fat in one's diet and the risk ofdeveloping a life threatening disease. Fats saturated with hydrogencause the body to produce more cholesterol which has been linked tocoronary disease known as atherosclerosis (plague build-up on arterywalls). Oil, composed mainly of polyunsaturated fats, in largequantities may increase the risk of cancer, and high fat diets generallyhave been scientifically linked to breast, colon, pancreas and prostatecancer. Importantly, fatty foods cause obesity. One reason is that ittakes less energy (fewer calories) to convert fat to stored fat cells inthe body than, other foods, such as, foods high in carbohydrates.

Fats and oils are now recommended by the U.S. government to be thesmallest part of one's diet and are to be used sparingly. Most majorhealth organizations now recommend that not more than thirty percent(30%) of the total calorie intake be from fat, and it has beenscientifically established that keeping the dietetic percent caloriesfrom fat below ten percent (10%) on average, not only helps to avoidobesity, coronary disease and certain cancers, but also, can actuallyreverse atherosclerosis over a long time period. The Food and DrugAdministration ("FDA") has now approved a new food label which willrequire listing the grams of fat and the calories from fat in the food.

One tablespoon of a vegetable oil contains 14 grams of fat, 126 caloriesand 100% of the calories are from the fat. Most common oils and fats arehigh in saturated fats and/or polyunsaturated fats.

Thus, it is now well recognized that one of the best choices of foods isa fat-free food. As defined by the FDA, fat-free means the food productmust have less than 0.5 grams of fat per serving. It is an object of thepresent invention to produce fat-free food products.

b. Potato Chips

Potato chips are a favorite snack food for all age groups.

Conventional potato chips are deep-fried in fat and are very high incalories. The typical finished potato chip contains 30-45% fat by weightand less than 5% moisture by weight (unless otherwise indicated by thecontext, all percentages of contents listed herein are by weight). Asingle one ounce (1 oz.) serving of any conventional potato chipcontains about 10 grams of fat, 150 calories and 60% of the calories arefrom the fat. Not only is the deep-fried process difficult to controland inefficient, often resulting in overcooked chips, but also, themoisture and fat left in the product react together to shortly impart arancid odor and flavor and loss of crispness which limits effectiveshelf life to about two weeks.

Because of the long term heavy emphasis on health and fitness and thestrong trend toward greatly reducing the amount of fat in the food weeat, there has been a long felt need for a fat-free potato chip snackfood product. It is an object of the present invention to producefat-free snack food products, including potato chips.

c. Prior Low Fat Or Fat-free Potato Chip Processes And Products

Having recognized the long felt need, other inventors have attempted,without success, to produce a commercially acceptable fat-free potatochip that looks, feels and tastes like a conventional fatty potato chipcooked in fat.

(1). Prior Processes Extracting Lipids From Deep-fat Fried Potato Chips

The earliest and most obvious way to reduce the fat content of thefinished potato chip product was to remove some of the oil absorbed bythe food pieces during the deep-fat fried step. Various techniquesincluded removing the pieces from the deep-fat frier while theirmoisture content was still relatively high (5-20%) and finishing heatingby a variety of techniques, such as, hot air drying (includingnon-recirculated air), radiant heating, microwave heating orcombinations thereof. These processes failed to produce a fat-freeproduct.

(2). Prior Low Fat Processes

The next early attempts to reduce the fat content of the finished potatochip were by completely eliminating, nullifying or limiting the durationof any necessary deep-fat frying of the potato pieces. In a process toYuan (U.S. Pat. No. 4,283,425) a single step of heating by microwave(910-915 mhz or 2400-2500 mhz) was used as the sole means to removemoisture and was alleged to produce a crispy, fat-free chip having theuniform color and taste of a deep fried potato chip. But, this productwas not commercially successful, probably because the actual appearanceand taste did not live up to its billing. Also, the non-standardequipment needed to make the product required significant investments.Moreover, optionally, the slices were dipped in or sprayed with anedible oil prior to final microwave cooking obviously to restore thatcharacteristic desirable deep-fat fried taste. The added fat content of3-5% by weight of this product equated to 0.85-1.43 grams per one ounce(28.5 gms.) serving, too high to be classified fat-free. Thus, thisproduct was basically a "low-fat" potato chip.

In another process to Haydock (U.S. Pat. No. 4,749,579) standard potatochip making equipment was used, but the potato slices were first saltedin depth, air dried and then preheated with infrared radiations beforedeep-fat frying. The finished "lite" potato chip product still had26-32% fat by weight, whereas "regular" potato chips had 36-42% fat byweight. In another variation to Neel (U.S. Pat. No. 4,933,199),par-fried slices were de-oiled to less than 25% fat by passingsuperheated steam through them in a controlled oxygen environmentfollowed by dehydrating to produce a finished potato chip having lessthan 2% moisture. In a still further variation of this process toProsise (U.S. Patent) the slices were first coated withpolyvinylpyrrolidone to provide increased resistance to oil absorptionduring the deep-fat frying step to produce a finished chip having 23%fat.

In still another process to Dreher (U.S. Pat. No. 4,756,916),monolayered potato slices were sprayed with a partially hydrogenatedcottonseed and soybean oil mixture, steam blanched, parabaked in a threezone oven at 425° F. (218° C.) to 15% moisture and final baked at 310°F. (155° C.) to 2% moisture producing a final potato chip having 10-18%fat by weight.

These products were not practical, fat-free and tasty.

(3). Prior Genuine Fat-Free Processes ((a)). Infrared-Microwave-Infrared

Finally, it also has been known to produce potato chips genuinelywithout the use of any form of cooking oil whatsoever. In a continuousprocess to August (U.S. Pat. No. 4,800,090) sliced potatoes were firstsubjected to an infrared (high intensity 4-6 micron wavelength) heatingstep to warm their exterior, then to a microwave energy (915-2450 mhz)heating step to warm their interior, and finally to another infrared(4-6 micron wavelength) heating step to brown them into a crisp,fat-free, potato chip snack food product that was low in calories andhad a long shelf life.

((b)). Microwave-Cold Water Rinse-Radiant Heat Batch

A further variation of a "no cooking oil" process was the batch processof Kloos (U.S. Pat. No. 4,906,483) in which the microwave cooking stepwas employed early in the process to activate the release of starchwhile the potato slices were still immersed in water followed by a coldwater rinse and final cooking in radiant heat until brown and crisp toproduce a fat-free potato chip.

((c)). Cooking Between Dual Relieved Opposed Surfaces

A still further fat-free process was to Childers (U.S. Pat. No.4,919,965) which simultaneously final cooked the potato slices bycompressing them between dual opposed heating surfaces which were 50%relieved driving the moisture into the voids in the cooking surfaces toproduce a fat-free potato chip.

None of the genuine fat-free processes have been commerciallysuccessful. Either the texture or taste of the product has beenunacceptable to consumers or the process was not continuous and thereforimpractical in large quantities.

Thus, the market still cries out for an economically made, tasty,genuine, fat-free potato chip product.

It is an object of this invention to fill this long felt need by makinga fully cooked fat-free potato chip product with a long shelf life thatlooks, feels and tastes like a conventional potato chip in an economicalcontinuous process without using any cooking oil whatsoever.

SUMMARY OF THE INVENTION

Set forth below is a brief summary of the invention in order to achievethe forgoing and other benefits and advantages in accordance with thepurposes of the present invention as embodied and broadly describedherein.

One aspect of the invention is in a continuous process for making acooked foodstuff without using any cooking oil including initial cookingmoist food slices wherein the improvement includes final cooking thefood slices in a dielectric heater by subjecting the slices to longwavelength radio frequency electromagnetic waves in an even controlledheating environment until the final moisture content is reached.

A further feature of this aspect of the invention is initially cookingthe slices in a three zone primary oven by first radiant heating theslices and then subjecting the slices to two successive stages of forcedair heating to reduce the moisture content of the slices to near a finalmoisture content.

Further features of this aspect of the invention include beginning withraw potato slices, independently controlling the time duration in eachof the three zones, simultaneously forcing the air into the top andbottom surfaces of the slices in the primary oven to a near finalmoisture content of about 15% by weight, independently controlling thetime duration of the slices in the dielectric heater to a final moisturecontent of about 7% by weight using wavelengths of about 65.8 feet at afrequency of about 15 mhz, and allowing the slices to successively,increasingly pile up in the last two forced air stages and thedielectric heating stage whereby a palatable, crisp, fat-free potatochip is produced having the texture and mouthfeel of a deep-fat friedpotato chip.

Another aspect of the invention is forming the slices by reciprocatingmeans holding the potatoes against a fixed cutting blade.

Other aspects of the invention include an apparatus for carrying out theprocess and the product made from the aforesaid process.

The present invention has the advantages of providing a fully cookedfat-free potato chip, that is low in calories, has a long shelf life andis made by a process that is easy to control and is economical tooperate while producing potato chips in commercial quantities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2A and 3 are front elevation views of the continuous process ofthe present invention shown partially in schematic form and partially insection along the lines 2A--2A of FIG. 2.

FIG. 2 is a top plan view of the three zone primary oven of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-3 show the preferred form of an apparatus for carrying out theprocess 10 of the present invention. In accordance with the presentinvention it has been determined that a fat-free potato chip can beproduced without deep-fat frying the potato pieces and yet stillmaintain a pleasant look, mouthfeel, texture and taste of the finishedproduct. The improved process utilizes a three zone primary oven--havingone radiant heat and two forced hot air stages for initial drying of theprepared monolayered potato slices to 7-15% moisture content--and then adielectric long wavelength radio frequency oven for final drying of thechips to 7% moisture content. A step-by-step description of the process10 and associated apparatus follows in which the numbers next to eachheading below correspond to numbered stations shown in FIGS. 1-3.

1. THE POTATOES

As shown in FIG. 1, the preferred starting materials are conventionalchipping potatoes 11, such as, Kennebec or Atlantic Chipping potatoes.Numerous other varieties will also work. Stones and other debris areremoved from the potatoes in a conventional mechanical destoner 12.

2. SCRUBBER

As shown in FIG. 1, the scrubber 13 is a conventional rotating drum withcounter rotating rollers along the outside which are covered with alight abrasive that cleans the skins of the potatoes without removingthe skin. If it is desired to remove the skins, the same piece ofequipment can be equipped with more abrasive rollers to accomplish thisstep. The scrubbed potatoes then pass to the washing step.

3. WASHER BIN

As shown in FIG. 1, the washer bin 14 is a vat of water that is used torinse any remaining debris from the scrubbed potatoes.

4. THE SLICER

As shown in FIG. 1, the slicer is shown generally as 15 in FIG. 1 andslices the potatoes to a preferable uniform thickness of 0.7-0.95millimeters depending upon specific market desires. Uniform thickness isimportant to maintaining even oven temperatures and thorough evencooking of each slice. The slicer 15 is a gravity fed, reciprocating bin16 which cooperates with a stationary blade 17 to achieve a monolayeringof the potato slices 24 on the moving conveyer belt 18. The belt speedis adjusted to achieve a preferential covering of about 85%-90% of theconveyer 18 with potato slices 24 ("product density"). The conveyer belt18 is a 6 feet wide mesh screen sized to allow small chip pieces andslicing debris to fall through and be carried away by conventional means(not shown). The speed of the belt will vary with the quantity ofthroughput and the size of the potatoes and desired product density.Next, the monolayered slices 24 are spray washed.

5. SPRAYER WASHER

The inclined, sprayer washer shown generally as 19 in FIG. 1 is a highpressured stream of water spraying the chips from equal angles 25 aboveand below the conveyer belt creating a squeegee action to remove excessstarch and moisture. Preferably spray washer 19 has multiple pairs ofspray streams 20-23. The angles 25 and force of the streams 20-23 areselected to achieve effective squeegee action without disturbing themonolayering and product density of the slices 24. The incline ofconveyer belt 18 further assists in the removal of the liquids andstarch. The potato slices 24 are now ready for cooking.

Although the invention is preferably practiced using raw potatoes whichare washed, peeled, sliced, monolayered and spray washed to destarchthem, other embodiments are possible. For example, peeling may beomitted, moving blade slicers may be used and other conventionaldestarching methods are known.

6-8. The Primary Oven

As shown in FIG. 2A, the primary oven 30 is a three zone cookingprocessor which includes a radiant oven 40 followed by two forced airconvection ovens 50, 60. The temperatures, air velocity and belt speedsare independently controllable in each phase to allow for maximumadaptability in accommodating the requirements of different varietiesand throughputs of potatoes 11.

The following specifications are for an apparatus which has the outputcapacity at the end of the dielectric heating step 70 to continuouslyproduce about 1000 lb./hr of finished potato product output. The totalinput capacity of the primary oven 30 necessary to continuously providethe aforesaid output varies with the variation in the moisture contentof the input potatoes 11. At 80% moisture of the potato slices 24, theinput capacity of primary oven 30 is about 4547.8 lbs./hr. in order toprovide a final output after the dialectic heater of about 1004.9lbs./hr. The passage from the primary oven 30 to the dielectric heater70 is enclosed to reduce the amount of lost heat during the transitionbetween ovens.

6. The Radiant Zone

As shown in FIG. 2A, monolayered slices 24 enter the input end ofradiant zone 40 by dropping onto belt 42, which is 6 feet wide, withoutdisturbing the monolayering. The radiant oven 40 heats the chips fromboth the top and the bottom by radiant, gas, high intensity, ceramicheaters 41 operating at approximately 1600° F. The length of this zoneis about 15 ft. The speed of the belt is about 30 ft. per minute. Theduration of slices 24 in this zone 40 is about 30 seconds at a productdensity of about 90% and a monolayered product depth of about 0.29inches. This step brings the right amount of glucose to the surface ofthe chips 24. Too little glucose will cause the chips 24 to dry out inthe next steps creating a powder on the surface, a scaly appearance,reduced chip snap, tough texture and an unpalatable taste. Too muchglucose removal will cause the chips 24 to have an extreme glazedappearance. The chips 24 next pass to the first forced air zone 50.

7. The First Forced Air Phase

As shown in the embodiment of FIG. 2A, the monolayered chips 24 enterthe first forced air zone 50 by dropping onto belt 51 which is 6 feetwide. Zone 50 is heated by gas burners 52, 62.

In zone 50 the use of forced air is considered very important to thedrying time of the potato chips 24. The forced air actually is driveninto the chips 24 to remove moisture at a rate which would takesignificantly longer in a solely convection or other standard oven. Fans53, 54 are shown mounted to the sides of the belt 51 in FIG. 2 butactually blow air into ducts 54a and 53a straddling the belt 51 andwhich exit directly onto the top and bottom, respectively, of the belt51. In zone 50 hot dry, recirculated air is thus blown directly into thetop and bottom surfaces of the chips 24 by zone 50 dry air recirculationfans 53, 54. The hot air from fans 53, 54 is simultaneously driven intothe top and bottom surface of the chips 24. The outer layers of thechips 24 are also dried so that they do not stick together in thesubsequent zones of the ovens 30, 70. The air is heated to a temperatureof about 410° F. with about 4200 cubic ft./min. of air directed towardthe top surface of the chips 24 and 6000 cubic ft./min. toward thebottom surface of the chips 24. The removed moisture is vented toexhaust through the top exhaust fans 65, 66 of the oven 30. A balancebetween exhaust and recirculation is achieved by trial and error basedon observation and test of the throughput product. The length of zone 50is about 16 ft. The belt 51 speed is about 20 ft./min. The zone durationis about 48 seconds. The product density is about 135%. Because belt 51is moving slower than belt 42, the product depth will vary during thisphase due to the curling and pile-up effects of the chips 24. The slices24 then pass to the third zone 60 of oven 30.

While fans 53, 54 are shown as side mounted with the exhaust fans 65, 66at the top, other configurations are possible in both forced air zones50, 60.

8. The Second Forced Air Phase

As shown in FIG. 2A the slices 24 enter the third zone 60 of the primaryoven 30 by dropping onto belt 61 which is 6 feet wide. Zone 60 is heatedby gas burners 52, 62. Zone 60 continues to dry the potato chips to nearfinal moisture content by forcing dry hot air into the top surfaces andbottom surfaces of the chips 24 using side mounted recirculating fans63, 64 shown in FIG. 2 which blow into bottom duct 63a and top duct 64ain the same manner as was done in zone 50. The air is heated to atemperature of about 350° F. with about 4200 cubic ft./min. of airdirected at the top surfaces and about 6000 cubic ft/min at the bottomsurfaces of the chips. The moisture is vented through the top of theoven by exhaust fans 65, 66 with balance achieved between exhaust andrecirculation as was done in zone 50. The length of this zone is longer,i.e., about 29 ft. The belt 61 speed is about 5.8 ft./min. The phaseduration is about 5 minutes (300 seconds). The product density is about465%. Again, because belt 61 is moving slower than belt 51, the slicescontinue to pile up and overlap, and the product depth grows toapproximately 3.5 inches. This final phase of the primary oven 30 driesthe potato chips 24 to approximately 15% moisture content. The chips 24then pass to the final cooking stage in dielectric oven 70.

Although it is possible to dry the chips in zone 60 to the final desiredmoisture content target of approximately 7%, it creates an unacceptable"sawdust taste". More than 15% moisture content will put additionalstrains on the production capacities of the dielectric heater 70 in thenext step.

9. Dielectric Heater (tandem unit)

As shown in FIG. 3, the chips 24 enter the dielectric oven or drier 70by dropping onto belt 71 which is about 6 feet wide. The dielectric oven70 uses long wavelength, radio frequency, electro-magnetic waves ofabout sixty-six (66) feet wavelength to create a controlled even heatwhich heats the chips 24 from deep inside the product in order to removethe remaining moisture to the desired 7% final moisture level.

Most dielectric heating is done at radio frequencies of 10-100 MHz. Thepreferred operating frequency range of the dielectric oven of thepresent invention is about 10-20 mhz which is in the high frequencyrange. A preferred frequency of about 15 mhz would have a wavelength of20 meters or about 65.8 feet (=(300×10^(6m) /sec÷15 mhz)×3.29 ^(ft) /m).Conventional microwave technology, such as is used in common homemicrowaves, uses a wavelength of 1.00 feet to 0.40 feet for operatingfrequencies of 915-2450 mhz, respectively, and creates an uneven poorlycontrolled heat which is unacceptable for the final heating stage of thecontinuous process of the present invention.

These long waves of the present invention can remove the highest levelof moisture content of the chips reaching oven 70 and thereby even outany variances in moisture content in the chips 24 in the dielectric oven70. The dielectric oven 70 uses two tandem mounted 20 kilowatt parallelplate (electrodes) high frequency fields schematically shown in FIG. 3as generator 74 and parallel electrode pairs 72-72a and, 73-73a, onefollowing the other. The belt 71 speed is variable and is selected sothat the depth of the potato slices is allowed to pile up until it isapproximately 7 inches, about double the depth of the product 24 in thesecond forced air zone 60 of primary oven 30. This bed depth in oven 70optimizes the moisture removal capability of dielectric heater 70. Thetime duration of the product in dielectric heater 70 is also variabledepending upon the desired moisture content of the chips 24 incoming toheater 70.

10. THE SEASONING UNIT

As shown in FIG. 3, the seasoning unit 80 is barrel shaped with twodistinct phases of operation. The first stage has sprayers 81 which add"Tack" for adhering the dry seasonings added in the second stage. Thetack may be maltodextrin, gum arabic, edible oil (up to the FDAregulated limit for fat-free) or other similar substances. Liquid flavorextracts and brine salt may be added at this phase. Fat-free substitutessimulating fat mouthfeel, if available, may be added. The second phasehas an auger 82 which applies dry seasoning to the potato chipsincluding salt and other seasonings such as Bar-B-Que, Sour Cream Onionand the like. Depending on plant layout and temperate zone in which itis located, a heat tunnel may be required to dry or cure the seasoningmix to the chips 24.

Belt 83 may be operated at any convenient speed to accommodate thethroughput of the line and bag and carton the finished chips 24.

11. FORM AND FILL

As shown in FIG. 3, a conventional machine (not shown) folds and moldsplastic film into bags 85 which are placed on conveyer belt 84. Theconveyer 83 drops measured amounts of the finished chips 24 into theplastic bags 85. The machine (not shown) seals the plastic bags 85.

12. CASE PACKING

As shown in FIG. 3, once the chips 24 are bagged they are placed intoboxes 86. These boxes are then moved to the warehousing area.

13. WAREHOUSE

As shown in FIG. 3, the finished chips 24 are produced in accordancewith anticipated orders. However since the chips have no oil and a lowmoisture content, they do not readily become rancid or lose theircrispness. Chips 24 have a storage/shelf life of 6 months or more.

The process 10 has been described with respect to making a potato chipsnack food product 24. However, with minor adjustments the process isequally capable of making other snack foods, including taco/tortillachips, formed potato chips, potato sticks, puffs and crisps, non-potatochips and puffs and similar snack food products.

The foregoing description of a preferred embodiment and best mode of theinvention known to applicant at the time of filing the application hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and obviously many modifications and variations arepossible in the light of the above teaching. The embodiment was chosenand described in order to best explain the principles of the inventionand its practical application to thereby enable others skilled in theart to best utilize the invention in various embodiments and withvarious modifications as are suited to the particular use contemplated.It is intended that the scope of the invention be defined by the claimsappended hereto.

We claim:
 1. An apparatus for continuously making a cooked foodstufffrom moist food slices without using any cooking oil comprising:a threezone primary oven for initially cooking the slices first by heating theslices in a radiant heating zone and then by further heating the slicesin two successive forced air heating zones to reduce the moisturecontent of the slices to near a final moisture content, and a cooker forfinal cooking the food slices by subjecting the slices to longwavelength radio frequency electromagnetic waves in an even controlledheating environment until a predetermined final moisture content isreached.
 2. The apparatus of claim 1 wherein the forced air heatingzones each further comprise:means for simultaneously forcing air intothe top and bottom surfaces of the slices.
 3. The apparatus of claim 2wherein the slices are fat-free potato slices and the oven for initialcooking further comprises:means for reducing the near final moisturecontent of the potato slices to a range of about 7-15% by weightwhereby, after final cooking, a palatable, crisp, fat-free potato chipis produced having the texture and mouthfeel of a deep-fat fried potatochip.
 4. The apparatus of claim 3 wherein the slices have top and bottomsurfaces and the three zone primary oven further comprises:means forforcing the air against the upper surfaces of the slices at a flowrateof about 4200 feet per minute and against the bottom surfaces of theslices at a flowrate of about 6000 fpm.
 5. The apparatus of claim 4further comprising:means for independently controlling the time durationof the slices in each of the three zones.
 6. The apparatus of claim 5wherein the cooker is a dielectric heater for final cooking whichfurther comprises:means for reducing the final moisture content of theslices to about 7% by weight.
 7. The apparatus of claim 1 wherein thethree zone primary oven further comprises:means for allowing the slicesto successively, increasingly pile up in the forced air heating stages.8. The apparatus of claim 1 wherein the forced air heating zones furthercomprise:means for simultaneously forcing air into the top and bottomsurfaces of the slices.
 9. The apparatus of claim 1 wherein the slicesare potato slices and the three zone primary oven for initial cookingfurther comprises:means for reducing the near final moisture content ofthe potato slices to the range of about 7-15% by weight.
 10. Theapparatus of claim 1 wherein the three zone primary oven furthercomprises:means for independently controlling the time duration of theslices in each of the three zones.
 11. The apparatus of claim 10 whereinthe means for independently controlling time further comprises:means forcontrolling the time duration in the first zone to about 30 seconds, inthe second zone to about 48 seconds and in the third zone to about 5minutes.
 12. The apparatus of claim 1 wherein the cooker is a dielectricheater which further comprises:means for independently controlling thetime duration of the slices in the dielectric heater to obtain a finalmoisture content of about 7% by weight.
 13. The apparatus of claim 12wherein the slices are potato slices and the three zone primary ovenfurther comprises:means for reducing the near final moisture content ofthe potato slices to a range of about 7-15% by weight whereby, afterfinal cooking, a palatable, crisp, fat-free potato chip is producedhaving the texture and mouthfeel of a deep-fat fried potato chip. 14.The apparatus of claim 1 wherein the cooker is a dielectric heater whichfurther comprises:means for piling up the slices in the dielectricheater to about double the depth of the slices in the three zone primaryoven.
 15. The apparatus of claim 1 wherein the cooker is a dielectricheater and the frequency of the waves is in the high frequency range.16. The apparatus of claim 15 wherein the frequency of the waves is inthe range of about 10-100 MHz.
 17. The apparatus of claim 16 wherein theoperating frequency is about 15 MHz and the wavelength is aboutsixty-six (66) feet.
 18. The apparatus of claim 1 wherein the cooker isa dielectric heater which further comprises:two tandomly mounted highfrequency fields.
 19. The apparatus of claim 18 wherein each of the twofields is about 20 kw output power.
 20. The apparatus of claim 1 whereinthe foodstuff is potatoes further comprising:reciprocating means forholding the potatoes against a fixed cutting blade to form the slices.21. An apparatus for continuously making a cooked foodstuff from moistfood slices without using any cooking oil comprising:a three zoneprimary oven for initially cooking the slices of the foodstuff having aradiant heating zone for a first heating step followed by two successiveforced air heating zones for further heating of the slices to reduce themoisture content of the slices to near a final moisture content, and acooker for finally cooking the food slices by subjecting the slices to acontrolled heating environment until a predetermined final moisturecontent is reached.
 22. The apparatus of claim 21 wherein the finalcooker has radio frequency electromagnetic waves.
 23. The apparatus ofclaim 21 wherein the forced air heating zones each furthercomprise:means for simultaneously forcing air into the top and bottomsurfaces of the slices.
 24. The apparatus of claim 23 wherein the slicesare fat-free potato slices and the oven for initial cooking furthercomprises:means for reducing the near final moisture content of thepotato slices to a range of about 7-15% by weight whereby, after finalcooking, a palatable, crisp, fat-free potato chip is produced having thetexture and mouthfeel of a deep-fat fried potato chip.
 25. The apparatusof claim 24 wherein the slices have top and bottom surfaces and thethree zone primary oven further comprises:means for forcing the airagainst the upper surfaces of the slices at a flowrate of about 4200feet per minute and against the bottom surfaces of the slices at aflowrate of about 6000 fpm.
 26. The apparatus of claim 25 furthercomprising:means for independently controlling the time duration of theslices in each of the three zones.
 27. The apparatus of claim 26 whereinthe cooker is a dielectric heater for final cooking which furthercomprises:means for reducing the final moisture content of the slices toabout 7% by weight.
 28. The apparatus of claim 21 wherein the forced airheating zones further comprise:means for simultaneously forcing air intothe top and bottom surfaces of the slices.
 29. The apparatus of claim 21wherein the slices are potato slices and the three zone primary oven forinitial cooking further comprises:means for reducing the near finalmoisture content of the potato slices to the range of about 7-15% byweight.
 30. The apparatus of claim 21 wherein the three zone primaryoven further comprises:means for independently controlling the timeduration of the slices in each of the three zones.
 31. The apparatus ofclaim 30 wherein the means for independently controlling time furthercomprises:means for controlling the time duration in the first zone toabout 30 seconds, in the second zone to about 48 seconds and in thethird zone to about 5 minutes.